Check out example codes for "css make a cell twice as big flexbox". It will help you in understanding the concepts better.

Code Example 1

.container {
  display: grid;
  grid-template-columns: 1fr 1fr;
  grid-gap: 10px;
}

.child.featured {
  grid-row-end: span 2;
}


/* non-essential decorative styles */
.container {
  padding: 10px;
  border: 2px solid gray;
  background-color: lightgray;
  height: 50vh;
}
.child {
  background-color: deepskyblue;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.3em;
}

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